Method and apparatus of growing a thin film

ABSTRACT

A method and apparatus of growing a thin film are provided. The method comprises at least (a) providing a number of substrates; (b) cleaning the substrates; and (c) placing the substrates into a reaction liquid; (d) vibrating the reaction liquid by ultrasonic waves such that a thin film is grown on the substrates evenly.

This application is a divisional application of co-pending applicationSer. No. 11/987,307, filed Nov. 29, 2007, which claims the benefit ofTaiwan application Serial No. 95148509, filed Dec. 22, 2006, the subjectmatter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a method and apparatus of growing athin film, and more particularly to a method and apparatus of growing aliquid-deposited thin film.

2. Description of the Related Art

The method of growing a thin film can be divided into two main classes:vapor phase deposition and liquid phase deposition. The vapor phasedeposition method has been widely applied to a semiconductor process andphotoelectric industry. However, owing that the vapor phase depositionmethod requires a series of vacuum procedures in an industrialmanufacturing process, it costs very much in hardware investment andmanufacturing, which affects its competitive advantage in applications.Therefore, it is necessary to develop low-cost thin film depositiontechnology. The liquid phase deposition thin film growing technology andequipment are taking an essential role due to the features of lowmanufacturing cost, a larger area of film deposition and less limitationto appearance of deposition carriers.

The conventional liquid phase deposition technology is low-temperaturedeposition technology, which is operated in a normal pressure and lowtemperature 30° C.˜90° C. without applying an external electric field.The substrate is dipped in a reaction liquid and combination anddeposition speed of the reactants can be controlled by adjustingreaction parameters of the reaction liquid to control to deposit a thinfilm on the surface of the substrate.

Referring to FIG. 1, a schematic diagram of a conventional thin-filmgrowing apparatus is shown. A conventional thin-film growing apparatus10 carries a constant-temperature sink 11 for controlling temperature ofthe reaction liquid through a heating stirrer 13. Theconstant-temperature sink 11 has a reaction-liquid trough 15 and astirring device 14 is placed in the reaction-liquid trough 15. Thestirring device 14 can be moved by the heating stirrer to stirring thereaction liquid in the trough 15 evenly. A pH-value detector 16 isdisposed in the reaction-liquid trough 15 for controlling pH-valueresponse of the reaction liquid. A substrate support base 12 isconnected to the constant-temperature sink 11 and is inserted in thereaction-liquid trough 15 for supporting a substrate 17 to function inthe reaction-liquid trough 15.

The liquid phase deposition thin film technology has two mechanisms onsubstrate surface deposition: (1) ion-by-ion mechanism in which ions ofthe reaction liquid grow the thin film directly on the surface of thesubstrate; (2) cluster-by-cluster mechanism in which ions of thereaction liquid are evenly compounded by cluster and then absorbed ontothe surface of the substrate to grow the thin film.

The thin film grown by ion-by-ion mechanism has advantages of beingthick, uniform, even and having high adhesion ability. However, anotherthin film grown through cluster-by-cluster mechanism in the liquid phasedeposition thin film technology has uneven thickness and lower adhesionability. Therefore, when a number of substrates are grown at the sametime in the liquid phase deposition technology, the range between thesubstrates will affect the quality of thin-film quality. Owing that therange of the substrates is related to the composition, theconcentration, the temperature, the pH-value of the reaction liquid andthe character of the substrate surface, if the equipment for carryingthe substrates can only carry the substrates by a constant range,variety and quality of the thin films grown on the substrates will belimited and thus applicability of the thin-film growing method will bereduced.

The thin films grown on the substrate in the conventional liquid phasedeposition technology includes a thin film of ion-by-ion mechanism and athin film of cluster-by-cluster mechanism, which worsens the quality ofthe thin film grown on the substrate.

Besides, when thin films are deposited on a number of substrates, therange between the substrates has to be adjusted according to compositionof the reaction liquid. The issues of substrate-range adjustment andpoor quality of thin film deposition both increase difficulty of processquality management, relatively reduce product throughout, and increaseproduction cost.

SUMMARY OF THE INVENTION

The invention is directed to a method and apparatus of growing a thinfilm. By using ultrasonic vibrator and adjusting a range between thesubstrates, the concentration, the temperature and the pH-value of thereaction liquid and repeatedly dipping, the thin film can be evenlygrown on the substrate with high adhesion ability, which can effectivelyimprove thin-film quality.

According to a first aspect of the present invention, a method ofgrowing a thin film is provided. The method comprises at least (a)providing a plurality of substrates; (b) cleaning the substrates; and(c) placing the substrates into a reaction liquid; (d) vibrating thereaction liquid by ultrasonic waves such that a thin film is grown onthe substrates evenly.

According to a second aspect of the present invention, an apparatus ofgrowing a thin film on a plurality of substrates is provided. Theapparatus comprises at least a reaction trough and an ultrasonicvibrator. The reaction trough is for containing a reaction liquid,wherein the substrates are placed into the reaction trough such that thereaction liquid grows the thin film on the substrates. The ultrasonicvibrator is for vibrating the reaction liquid by ultrasonic waves.

The invention will become apparent from the following detaileddescription of the preferred but non-limiting embodiments. The followingdescription is made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional thin-film growingapparatus.

FIG. 2A is a top view of a thin-film growing apparatus according to apreferred embodiment of the invention.

FIG. 2B is a front view of a thin-film growing apparatus according to apreferred embodiment of the invention.

FIG. 2C is a lateral view of a thin-film growing apparatus according toa preferred embodiment of the invention.

FIG. 3 is a schematic diagram of a thin-film growing method according tothe preferred embodiment of the invention.

FIG. 4 is a schematic diagram of the carrying unit of FIG. 2B.

FIG. 5 is a XRD analysis diagram of a semiconductor thin film AgIn₅S₈according to the preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a method and apparatus of growing a thin film. Areaction liquid is used as a forerunning substance for thin filmdeposition. By using ultrasonic waves to vibrate the reaction liquid,separate the small cluster-by-cluster particles and help the ion-by-ionparticles to grow the thin film, the thin-film quality can be improved.In the following description, the method and apparatus of growing thethin film will be illustrated in details as embodiments. However, theembodiments will not limit the scope of the invention. The invention isnot limited to the mode described in the embodiments.

Referring to FIGS. 2A-2C, a top view, front view and lateral view of athin-film growing apparatus according to a preferred embodiment of theinvention are shown respectively. A thin-film growing apparatus 300 ofthe embodiment includes a reaction trough 310, ultrasonic vibrators 312and 313, a carrying unit 340, a number of cleaning troughs 311, ashifting unit 320 and a liquid input device 370. The reaction trough isfor carrying a reaction liquid. The substrates 360 (shown in FIG. 4) areplaced into the reaction trough 310. The ultrasonic vibrator 312 isdisposed at the lower part of the reaction trough 310. The ultrasonicvibrator 312 is for vibrating the reaction liquid by ultrasonic waves soas to grow a thin film on the substrates 360. The carrying unit is forcarrying the substrates 360. The several cleaning troughs 311 are placedin front of the reaction trough 310 for cleaning the substrates 360 byusing the ultrasonic vibrator 313 before growing. The shifting unit 320is disposed at the upper part of the reaction trough 310 and connectedto the carrying unit 340 to move the carrying unit 340 in each cleaningtrough 311 and the reaction trough 310. The liquid input device 370 isused to input liquid in a constant amount to each cleaning trough 311and the reaction trough 310. The parameter adjusting unit 350 is usedfor adjusting the temperature, the concentration and the pH-value of thereaction liquid.

Referring to FIGS. 2A˜2C and FIG. 3 at the same time, wherein FIG. 3 isa schematic diagram of a thin-film growing method according to thepreferred embodiment of the invention. In step 301, provide thesubstrates 360. The substrates 360 are carried by the carrying unit 340and separated at a constant range a (as shown in FIG. 4). Referring toFIG. 4, a schematic diagram of the carrying unit 340 of FIG. 2B isshown. The substrates 360 are carried by the carrying unit 340 by aconstant range a. The carrying unit 340 includes a frame 341, a numberof lower separation plates 342 and upper separation plates 343, aseparation positioning plate 344 and a positioning device 346.

The lower separation plates 342 are coupled to the lower end of theframe for fixing the lower ends of the substrates 360 by the constantrange a. The upper separation plates 343 are coupled to the upper end ofthe frame 341 for fixing the upper ends of the substrates 360 by theconstant range a. The carrying unit 340 can change the constant range aof the substrates 360 by adjusting the upper separation plates 343 andlower separation plates 342 according to the composition, concentration,temperature, a pH-value of the reaction liquid and surface features ofthe substrates 360. Besides, the upper separation plates 343 and lowerseparation plates 342 can be adjusted simultaneously to have the sameconstant range a to maintain the substrates 360 arranged in parallel.

The separation positioning plate 344 is disposed at one side of theframe 341. The separation positioning plate 344 includes at least asliding groove 345 and a positioning device 346. The upper separationplates 343 and lower separation plates 342 slide along the slidinggroove 345. The positioning device 346 is for adjusting and positioningthe positions of the upper separation plates 343 and lower separationplates 342 in the sliding groove 345 such that the relative positions ofthe upper separation plates 343 and lower separation plates 344 fit inwith the size of the substrates 360. Therefore, the carrying unit 340 ofthe embodiment can be applied to various sizes of substrates 360.

Moreover, the carrying unit 340 can adjust the range a of the substrates360 through the upper separation plates 343 and lower separation plates342, wherein the range a is between 0.5 mm and 10 mm. In the embodiment,the carrying unit 340 adjusts the range a of the substrates 360 to be 3mm. When a thin film is to be grown on a number of substrates 360, therequired range of the substrates 360 is related to the composition ofthe reaction liquid. For this reason, the carrying unit 340 is designedto have function of adjusting the range of the substrates 360, and thuscan be applied to various reaction liquid, which can effectively reducemanufacturing cost.

In additions, referring to FIGS. 2A˜2C at the same time, the carryingunit 340 is moved by the shifting unit 320 in the thin-film growingapparatus 300. The shifting unit 320 consists of a shift combinationframe 321, transverse shift motor 322, a line of gear wheels 323, anelevating motor 324, a screw shaft 325 and a unit connection frame 326.The unit connection frame 326 is coupled to the carrying unit 340 andthe shifting unit 320 moves the carrying unit 340 according to a controlcommand.

Next, in step 302 of FIG. 3, the shifting unit 320 moves the carryingunit 340 and placing the carried substrates 360 into the severalcleaning troughs 311. The cleaning troughs 311 contain a cleaning liquidfor cleaning the substrates 360. The ultrasonic vibrator 313 is disposedat the lower part of the cleaning troughs 311 to increase a cleaningeffect of the cleaning liquid. The cleaning procedure of the embodimentis to clean by ethanol, deionized water, acetone and deionized water insequence. The impurities on the surface of the substrates 360 can beremoved by using the ultrasonic vibration to increase a cleaning effect.

Afterward, in step 303 of FIG. 3, adjust the reaction parameters, suchas the concentration, the temperature, the pH-value of the reactionliquid. In the embodiment, the reaction liquid is at least consisted offirst liquid and second liquid. The first liquid is consisted ofmonovalance metal ions and trivalence metal ions or consisted ofmonovalence metal ions, trivalence metal ions and di-valence metal ions.Moreover, the first liquid is consisted of nitric acid, sulfuric acid,acetic acid, phosphoric acid or the halogens and indium (In), sodium(Na), potassium (K), magnesium (Mg), calcium (Ca), strontium (Sr),aluminum (Al), gallium (Ga), antimony (Sb), copper (Cu), silver (Ag),zinc (Zn), iron (Fe), platinum (Pt), titanium (Ti), zirconium (Zr),niobium (Nb), tantalum (Ta), manganese (Mn), ruthenium (Ru), nickel(Ni), cadmium (Cd) or wolfram (W). The second liquid is sulfuric-ionliquid, and consisted of sulfuric ions provided by sulfur acetylateamine (CH₃CSNH₂).

In the embodiment, the thin film is exemplified to be a thin film ofsemiconductor sulfide consisted of silver indium sulfide (AgIn₅S₈). Thereaction liquid of the embodiment is a mixture of the first liquid andsecond liquid. The first liquid includes 0.1˜1 M of silver ions (Ag⁺)and indium ions (In³⁺) and 6.4˜8.4 M of triathylate amine (C₈H₁₅NO₃).The second liquid includes 0.1˜1 M of sulfuric ions (S²⁻). The mixturevolume ratio of the first liquid and the second liquid is 1:1˜1:20, andthe pH value of the reaction liquid is 1˜3. The temperature of thereaction liquid is controlled to be between 40° C. and 90° C.

Preferably, the first liquid includes 0.4 M of mixture liquid of silvernitrate (AgNO₃) and indium nitrate (In(NO₃)₃) and 7.4 M of triathylateamine (C₆H₁₅NO₃) as a source of positive ions (Ag⁺, In³⁺) of thereaction liquid. The second liquid includes 0.4 mole of sulfur acetylateamine (CH₃CSNH₂) as a source of negative ions (S²⁻). The mixture volumeratio of the first liquid and second liquid is 1:7 and sulfuric acid isused to adjust the pH-value of the reaction liquid to be between 1.5 and2. In the meanwhile, the temperature of the reaction liquid iscontrolled to be 80° C.

As shown in FIGS. 2A˜2C, the parameter adjusting unit 350 is disposed inthe reaction trough 310 and includes a sensor 351 and aconstant-temperature equipment 352. The sensor 351 is for adjusting theconcentration and the pH-value of the reaction liquid and theconstant-temperature equipment 352 is for adjusting and maintaining thetemperature of the reaction liquid. When the thin-film growing method isperformed, the parameter adjusting unit 350 can effectively control thereaction environment of the reaction liquid to stabilize the parametersfor thin film deposition. The chemical reaction formulas of the reactionliquid are shown as below.

CH₃CSNH₂+H⁺→H₂S—CH₃CNH⁺  (1)

H₂S+H₂O→HS⁻+H₃O⁺  (2)

HS⁻+H₂O→S²⁻+H₃O⁺  (3)

The whole chemical reaction formula is as follows:

Ag⁺+(5−4x)In³⁺+(8−6x)S²⁻ →xAgInS₂/(1−x)AgIn₅S₈ ,x=0˜1  (4)

Besides, referring to FIGS. 2A and 2B, the liquid input device 370 is incharge of providing the above reaction trough 310 and cleaning trough311 with the reaction liquid and cleaning liquid. The liquid inputdevice 370 includes a control valve unit 371 of cleaning liquid andreaction liquid, setting bump 372 and the reaction liquid storage tank373. The control valve unit 371 sends out a control command to controlthe setting bump to bump the reaction liquid from the storage tank 373into the assigned reaction trough 310 and bump the cleaning liquid fromthe cleaning liquid storage tank (not shown in the figure) into theassigned cleaning trough 311. The liquid input device 370 can releaseliquid of the troughs through a liquid releasing pipe (not shown in thefigure) according to the control command.

Then, in step 304 of FIG. 3, when the parameters of the reaction liquidof the reaction trough 310 is adjusted by the parameter adjusting unit350, the carrying unit 340 is moved by the shifting unit 320 to placethe substrates 360 into the reaction trough 310.

Following that, in step 305 of FIG. 3, vibrate the reaction liquid byultrasonic waves to generate reaction of the liquid and grow a thin filmon the substrates 360. The ultrasonic vibrator 312 is disposed at thelower part of the constant-temperature equipment 352 of the reactiontrough 310 and the vibration frequency of the ultrasonic waves is 20kHz˜120 kHz. The reaction liquid is vibrated in this vibrating frequencyfor 30 minutes to grow the thin film on the substrates 360. Theultrasonic waves for vibrating the reaction liquid have the followingtwo functions. One is to mix evenly the reaction liquid. The other is toshake out the cluster-by-cluster particles absorbed by the substrates360 from the surface of the thin film and help the ion-by-ion particlesto grow the thin film to achieve the purpose of selective deposition. Inthis way, the thin film grown can be thick, firm, even and have highadhesion ability.

Next, in step 306 of FIG. 3, determine whether a number of performingthe substrate growing operations reaches a predetermined number. If no,repeat the steps 303 and 305. The predetermined number is 1˜10. In theembodiment, the steps 303˜305 are repeated four times for growing thesubstrates 360 to complete the thin film growing method.

Referring to FIG. 5, a XRD analysis diagram of a semiconductor thin filmAgIn₅S₈ according to the preferred embodiment of the invention is shown.The crystal composition of the thin film AgIn₅S₈ is analyzed by a XRDmethod. The sample of the XRD analysis diagram is a thin film productionof the embodiment. The thin film production is a thin film AgIn₅S₈processed by four times of growing. After burning the thin film with550° C. argon in a pipe-like stove for one hour, the thin film has astructure of stereotyped cubic-type AgIn₅S₈ phase, which has an eventhickness and high adhesion ability. Therefore, the invention canimprove thin-film quality of liquid phase deposition by vibrating thereaction liquid with ultrasonic waves and growing repeatedly.

Besides, a number of reaction troughs can be disposed in series in thethin-film growing apparatus of the invention to perform a number ofgrowing processes according to process requirement in addition torepeating a growing process by using a single reaction trough.

The method and apparatus of growing a thin film disclosed by the aboveembodiment can not only improve thin-film quality by ultrasonicvibration, but also improve the drawback of the thin film with uneventhickness and poor adhesion ability in the liquid phase depositionmethod. Moreover, the optimal thickness and quality of the thin film canbe obtained by using the carrying unit to adjust the range of thesubstrates and repeatedly growing. The chemical thin film depositionmethod is a well-known industrial process and has the advantages oflower production cost and limitation of appearance of depositioncarriers. Therefore, the invention can improve the drawback of theconventional chemical deposition method and reduce the production cost.

While the invention has been described by way of example and in terms ofa preferred embodiment, it is to be understood that the invention is notlimited thereto. On the contrary, it is intended to cover variousmodifications and similar arrangements and procedures, and the scope ofthe appended claims therefore should be accorded the broadestinterpretation so as to encompass all such modifications and similararrangements and procedures.

What is claimed is:
 1. An apparatus of growing a thin film on aplurality of substrates, comprising: at least a reaction trough, forcontaining a reaction liquid, wherein the substrates are placed into thereaction trough such that the reaction liquid grows the thin film on thesubstrates; and an ultrasonic vibrator, for vibrating the reactionliquid by ultrasonic waves.
 2. The apparatus according to claim 1,further comprising: a carrying unit, for carrying the substrates by aconstant range.
 3. The apparatus according to claim 2, wherein thecarrying unit comprises: a frame; a plurality of lower separationplates, coupled to a lower end of the frame for fixing lower ends of thesubstrates by the constant range; and a plurality of upper separationplates, coupled to an upper end of the frame for fixing upper ends ofthe substrates by the constant range.
 4. The apparatus according toclaim 3, wherein the carrying unit can adjust a range of the lowerseparation plates and a range of the upper separation plates such thatthe constant range is 0.5 mm to 10 mm.
 5. The apparatus according toclaim 3, wherein the carrying unit further comprises: a separationpositioning plate, positioned at one side of the frame and having asliding groove, wherein the upper separation plates and the lowerseparation plates slide along the sliding groove; and a positioningdevice, for adjusting and positioning positions of the upper separationplates and the lower separation plates in the sliding groove such thatrelative positions of the upper separation plates and the lowerseparation plates fit in with size of the substrates.
 6. The apparatusaccording to claim 1, further comprising: a plurality of cleaningtroughs, for carrying a cleaning liquid for cleaning the substrates. 7.The apparatus according to claim 1, further comprising: a parameteradjusting unit, for adjusting the concentration, the pH-value and thetemperature of the reaction liquid.
 8. The apparatus according to claim1, further comprising a plurality of reaction troughs for performing aplurality of film growing operations.